


Better the Devil You Know

by Kindassunshine



Category: Ao no Exorcist | Blue Exorcist
Genre: Anal Sex, Angst, Demons, M/M, Rough Sex, Tails, Voyeurism
Language: English
Status: Completed
Published: 2014-08-09
Updated: 2014-08-09
Packaged: 2018-02-12 11:02:16
Rating: Mature
Warnings: Underage
Chapters: 1
Words: 1,629
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2107371
Author URL: https://archiveofourown.org/users/Kindassunshine/pseuds/Kindassunshine
Summary: <blockquote class="userstuff">
              <p>Being the son of Satan is causing Rin more difficulties than expected and Yukio is determined to keep his brother safe, even if it means making a deal with the Devil and asking the Earth King for the unspeakable.</p>
            </blockquote>





	Better the Devil You Know

**Author's Note:**

> Hi! I really like this series :) the manga is gorgeous, not so sure about the anime but you can't have everything...
> 
> Also I have tried not to spring on you/completely mangle any Japanese in the making of this fic that being said I do like honorifics :D seriously I think we should have them in English. Enjoy!

Yukio and Rin looked up as they heard the door click open. Mephisto gave a flamboyant bow, revealing the person stood behind him. Yukio’s hand moved to his holster without missing a beat.  
‘Now, now that’s not very friendly Okumura-kun,’ Mephisto grinned, setting his hat down on Yukio’s desk. Shedding his cloak, he turned to Amaimon. Yukio looked at Amaimon too.  
‘Do you understand what you have to do?’ Mephisto asked, dispassionately waving a gloved hand at Rin, who looked down at his bare feet.  
‘Yes,’ he frowned, ‘but why me?’  
‘Why not you?’ Mephisto countered cheerfully. Rin and Amaimon blinked at one another stunned by this flawless logic.  
‘I really don’t think-’ Yukio started; he could think of at least twenty-five reasons why this was a bad idea.  
‘Do you remember the conditions, under which, I agreed for you to be present at this little consensus ad idem, Okumura-kun?’ Mephisto purred, flashing a sharp grin. Yukio pressed his lips together.  
‘I do, Sir, but with respect-’  
‘Why do people always say that when they are not respecting my wishes?’ Mephisto sighed settling himself into a recently materialised armchair. Yukio hesitated.  
‘Yukio...’ Rin muttered from his seat on the bed. Yukio stiffly pulled out the desk chair and sat on it.  
‘Go ahead,’ Mephisto smiled at Amaimon, who had been staring blankly at the pointed toes of his boots. Now he moved to the bed. Yukio felt his neck prickle. Amaimon’s host looked maybe two or three years older than him and very unhealthy. A hand settled on his wrist and he looked up. Mephisto didn’t look at him instead he narrowed his eyes at the two boys on the bed.  
‘No biting, no scratching, no flames, are you listening Okumura-kun?’ he looked thoughtful, ‘can you think of anything else, sensei?’ he said turning to Yukio, who looked sternly at his brother. Rin gave a slight nod.  
‘I assume he has no transferable diseases,’ Yukio asked, eyeing Amaimon’s unkempt appearance.  
‘Certainly not,’ Mephisto smirked then nodded to his younger brother. Amaimon threw a leg over Rin and pushed him onto his back in a single fluid movement. Yukio half stood as Amaimon delivered a sloppy open mouthed kiss and Rin squeaked.  
‘Please calm down, Okumura-kun,’ Mephisto said hand tightening on Yukio’s wrist pulling him back. Yukio regained his seat and silence ensued save for slurping, rustling sounds. Peeking at the couple on the bed, Yukio noticed that Amaimon kissed with his strange blue eyes wide open. He felt himself flushing as the demon slid a hand in between their bodies. Rin groaned kissing harder. Amaimon growled grinding his hips firmly into the others. Rin moaned arching his back as Amaimon kissed down his neck. Yukio was beginning to wish very fervently that the floor would swallow him up. He glanced at Mephisto, who looked at his ease with a pink boot resting on his knee. They twined around one another, there was a ripping sound. A furry black tail flicked as Rin rolled to straddle the other. He hissed, showing Amaimon his long canines, the other licking them with a pointed tongue. They rolled again. Rin was pressed securely into the mattress. Pinning his hands, Amaimon popped his belt buckle and unzipped his jeans one-handed. The demon stilled leaning his forehead on Rin’s. Rin screamed, teeth flashing.  
‘So loud, child,’ Amaimon murmured, ‘how you must suffer being in this human skin...’ he bit Rin’s chin for emphasis. Rin licked his mouth, while Amaimon held his dark head in place staring into his eyes, knees coming up. Yukio tried to stand again but Mephisto held him.  
‘W-what is he doing?’ Yukio whispered. Mephisto smiled.  
‘You’re not an Aria, are you? I suppose you wouldn’t guess from his name,’ he patted Yukio’s arm, ‘you know that isn’t going to work,’ he called louder. Amaimon sat up regarding him blankly.  
‘Always works,’ he muttered pulling unashamed on his cock, looking down at Rin head tipped to the side. Yukio looked at the floor. A rasping laugh.  
‘You can look, don’t be shy,’ Amaimon purred, Yukio felt his face throbbing, ‘why won’t it work?’ he growled after a minute.  
‘Think about, it doesn’t work on father does it?’ Mephisto muttered. Amaimon snorted and tipped his head back until his hair touched his heels. His back clicked. Yukio bit his lip watching the unpleasant contortion.  
‘This one isn’t going to last much longer,’ he sighed.  
‘Too young,’ Mephisto agreed.  
‘I don’t want a decrepit one like yours, Older Brother,’ he smirked. Mephisto snorted. Amaimon clicked his neck then lent over Rin again, kissing him thoroughly. He broke the kiss unexpectedly and flipped Rin onto his stomach. Tugging the tail out of the way, he pulled Rin’s underwear down his legs. Rin screeched as Amaimon joined their bodies in a single thrust. Mephisto grabbed Yukio again. Rin was quiet now except for low growls that rumbled through his chest. Amaimon was growling too, his movements were unexpectedly smooth. Soon Rin had his head tucked in his arms and was struggling to spread his legs more. The tail twisted between Amaimon legs until he grunted and unfurled his own. The black tail instantly entwined its self in the other. Mephisto shifted slightly and Yukio glanced at him. Rin whined squirming as Amaimon held him still, as his thrusting became more intense. Rin seemed to be trying to twist loose but then he groaned going limp. Amaimon gave a final thrust arching his back, ejaculating with a soundless scream. Mephisto applauded. Amaimon pulled out, carefully untwisting his tail from the other. Rin rolled onto his side stretching contently as Amaimon climbed off him tucking his appendages away.  
‘Go and have a shower, Okumura-kun,’ Mephisto ordered as Rin sat up.  
‘Yeah, yeah,’ Rin muttered dragging himself into the bathroom. Yukio stood, making to follow him but Mephisto caught his wrist.  
‘He’ll heal on his own and he won’t want you messing with him at the moment,’ he murmured perceptively. Amaimon glanced at his brother then eyed Yukio.  
‘I haven’t lain with a human in years,’ he said idly from the bed, ‘they’re so... delicate.’  
‘That one is off limits I’m afraid,’ Mephisto smiled patting Yukio’s shoulder, ‘as are any others within the walls of this city, my dear brother,’ he purred.  
‘Thank you, Sir, but I’m perfectly capable of defending myself,’ Yukio told him curtly. Mephisto chuckled beckoning to his brother.  
‘Come now, I’ll show you out,’ he said neatly inserting a key into the bedroom door and opening it to reveal a drafty terrace. Amaimon got up reluctantly still watching Yukio.  
‘Now,’ Mephisto snapped crisply. Amaimon stalked towards the door, speaking in a rasping language as they drew level.  
‘You shouldn’t be speaking that in here!’ Yukio barked, as the two demons peered at him. Mephisto laughed again.  
‘Quiet right. Wouldn’t want to attract that sort of attention,’ he chuckled, ‘no doubt our father will get it out of you anyway.’ He sighed, Amaimon shrugged in response. Mephisto caught his arm leading him through the door, whispering in his ear. Yukio sat wearily as the door closed with a click. Now it was over, Yukio wasn’t so sure he had acted in the right way.  
‘Well,’ Mephisto grunted flopping into his armchair.  
‘Will it work?’ Yukio asked softly, even thought he could still hear the water in the bathroom.  
‘It certainly should take care of any unhealthy urges,’ he smiled, ‘and if the problem arises again, we simply repeat the process.’ He made an expansive gesture.  
‘I still don’t,’ he bit his lip, ‘don’t understand why it couldn’t have been you.’ Mephisto sniffed with dignity.  
‘You are asking why I, your superior and guardian, was unable to perform this task? My goodness I thought you were the intelligent one!’ he gave a musical laugh. Yukio glared at him.  
‘Don’t give me that,’ he muttered, ‘I know what you are.’  
‘And I know what you are,’ Mephisto flashed his teeth.  
‘What I’m saying is, there must be another reason...’ Yukio looked at him closely. Mephisto gave him an assessing look.  
‘You are too young to know half the reason,’ he laughed, ‘Rin-kun is our father’s present obsession. Attending to him is tantamount to currying favour.’ His expression darkened.  
‘So you’re letting the Earth King do it instead?’ Yukio asked confused.  
‘He’s still immature and stupid,’ Mephisto waved absently, ‘there is no harm in letting the young ones rut.’ Yukio flushed. He’d never expected to be involved with his brother’s sex life but he wasn’t going to leave Rin alone with the Earth King and Mephisto.  
‘You’re attending to him anyway, aren’t you?’ Yukio muttered. Mephisto smiled.  
‘I am using my power and influence to protect and nurture him,’ he declared grandly, ‘and they know it. That is why I’ve locked him up in my school,’ he chuckled. Yukio arched his eyebrows.  
‘We’re your prisoners?’ He teased. When Mephisto got worked up he showed a much stronger resemblance to Rin. Mephisto snorted.  
‘What are you talking about?’ Rin asked as he sloped into the room wreathed in steam.  
‘Nothing much,’ Yukio said cheerily, ‘you can share with me if you like,’ he added as Rin looked at the untidy bed and went a little pale. Rin grinned and settled himself in his twin’s bed. Mephisto slunk over and perched on the bed.  
‘Don’t,’ Rin muttered voice slightly high-pitched.  
‘You’ll sleep much better this way,’ Mephisto murmured, ‘have all your wounds healed?’ Rin grunted assent. Mephisto lent over him murmuring in German. After a moment Yukio heard a soft snore and Mephisto hopped up.  
‘I’ll leave you to it, Okumura-sensei,’ he said bowing, and then twirling another key in the door vanished into a room Yukio recognised as his office.


End file.
